Let me preface this I am asking for advice backed up with empirical evidence. I know that a lot of people have great opinions about stuff. I am trying to understand somethings. Okay I am probably going to bite the bullet and buy a new Ram 2500 with the 6.7L Cummins. I know that it’s recommended to run 10W30 but in the winter recommend 5W40. I really don’t want to change oil in October just to change it again in April. Summer temperatures are triple digits yet winter temperatures get below 0 for a while. Is it safe to run 5W40 year around even in 100 degree weather. I know there’s someone who probably has and that’s fine but they aren’t making my truck payment. So please respond with evidence based responses. Thanks and I am not going into a debate on Rotella v Valvoline. I know Cummins recommends it while Ram recommends Rottela only because Rottela has a contract with dealerships service departments. So I think either one is fine.